It would be very hard to say which board is tough or easy. But if you go for CBSE board, you would be better placed as the syllabus is common throughout the country. Moreover, the maths and science syllabus of the CBSE board is in sync with competitive examinations.
But if your focus is more towards state entrances, the state board would be better as it will cover the maximum syllabus of the exam.
I hope this information helps you
All the best